Iranian President Hassan Rouhani left Monday for a visit to Europe. The trip was billed as being “of prime importance” after the US pulled out of the 2015 nuclear deal between Tehran and world powers. Rouhani was heading for Switzerland and scheduled to travel on to Vienna on Wednesday, where the nuclear deal was signed in July 2015. The visit will be an “opportunity to talk about the future of the [nuclear] agreement,” Rouhani said at Tehran’s Mehrabad Airport. Tehran is continuing intense negotiations “to find a way to preserve this agreement,” AFP quoted Iran’s Foreign Ministry spokesman Bahram Ghassemi as saying.